1. Field of the Invention
The C.sub.2-4 -alkanolamine salts of alkenyl succinic acid dialkyl semiamides are used as corrosion inhibitors in aqueous systems.
2. Statement of the Related Art
Numerous derivatives of succinic acid have already been proposed as corrosion inhibitors. Thus, U.S. Pat. No. 2,490,744 describes reaction products of alkenyl succinic acid anhydrides with primary amines in a molar ratio of 1.25-2:1 as rust inhibitors in lubricating oils and certain organic solvents, the total number of carbon atoms in 2 mols of the anhydride and 1 mole of the amine being between 28 and 50.
Reaction products of alkenyl succinic acid anhydrides with long-chain dialkylamines are similarly known for use in the oil phase. U.S. Pat. No. 3 546 151 describes inter alia the reaction products with excess ditallow amine. The wax-like succinic acid semiamide amine salts obtained may be used as corrosion inhibitors in water-repellent media.
The use of alkanolamine salts of C.sub.8 -C.sub.9 -alkenyl succinic acid for rust prevention in purely aqueous systems is known from German Patent Application No. 29 43 963.
In addition, the use of amidomaleic acid alkanolamine salts containing a C.sub.8 -C.sub.12 -isoalkyl group on the amide radical as corrosion inhibitors in aqueous systems is described in European Pat. No. 2,780.
The proposed alkanolamine salts of C.sub.8-9 -alkenyl succinic acid or amidomaleic acid are distinguished by the fact that they only foam to a minimal extent. However, their anticorrosive properties are unsatisfactory.
U.S. Pat. No. 4,207,285 discloses modified maleic acid corrosion inhibitors for aqueous systems, including the triethanolamine salt of maleic acid mono-2-ethylhexylamide. The corresponding succinic acid compound is used in a comparative example and is disclosed as unsatisfactory. None of the disclosed compounds are alkenyl substituted.